This little boost charger has been surprisingly fun to work on. It has two different ST Microelectronics parts: the SPV1040 energy harvester, and the STM32L072 microcontroller.
It’s capable of accepting and regulating up to roughly 10VA of power (5.5V and 1.8A are its upper bounds), but it can efficiently boost and store even half a volt at just a few milliamps.
It can be configured for many battery chemistries, and has current-limit and voltage-limit safety features suitable for lithium batteries.
I’m using the MCU’s low-speed clocks, stop modes, and analog comparators to conserve as much power as possible. Why add an MCU at all? Two features which the SPV1040 does not have:
- automatic day/night switching, and
- undervoltage lockout, to switch off the load if a LiPo cell drops below 2.7V, the point at which degradation begins
Naturally, right around the time I got this SPV1040 board humming along really well, ST introduced the SPV1050, which does indeed have those features. Ah well. Time to get started on the sequel, I suppose…
I hope to publish quite a few project pages about the development and uses of this little board in the weeks and months ahead. Stay tuned!